In a domestic photovoltaic power generating system where power generated by a generator such as a solar panel is used, power is controlled by a power conditioner. For example, Patent Document 1 (identified below) describes an example of power conversion equipment preferably used in such a power conditioner. The power conversion equipment described in Patent Document 1 includes a current resonant converter. A switching frequency is changed to obtain a switching frequency at which the highest power conversion efficiency is achieved. By so doing, a switching frequency corresponding to the resonant frequency of the current resonant converter is detected, and the detected frequency is set. This decreases switching loss and noise and improves efficiency.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2014-217199.
In the power conversion equipment described in Patent Document 1, even if the leakage inductance of a transformer and the capacitance of a resonant capacitor deviate from respective design values, which causes a resonant frequency to deviate from a design value, an optimal switching frequency can be set. However, according to the equipment described in Patent Document 1, a switching frequency is set so that the highest power conversion efficiency is achieved. Thus, unless predetermined conditions such as controlled input/output power are met, a switching frequency cannot be set.